Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings C h a p t e r 29 Development and Inheritance PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Development  Embryological Development  Occurs during first 2 months after fertilization  Study of these events is called embryology  Fetal Development  Begins at start of ninth week  Continues until birth

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Development  Prenatal Development  Embryological and fetal development stages  Postnatal Development  Commences at birth  Continues to maturity when aging process begins

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fertilization  Fertilization  Fusion of two haploid gametes, each containing 23 chromosomes  Produces zygote containing 46 chromosomes Fertilization and the Preparation for Cleavage

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fertilization  Acrosomal Caps  Release hyaluronidase and acrosin  Penetrate corona radiata, zona pellucida, toward oocyte surface  Oocyte Activation  Contact and fusion of cell membranes of sperm and oocyte  Follows fertilization  Oocyte completes meiosis II, becomes mature ovum

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fertilization  Polyspermy  Fertilization by more than one sperm  Prevented by cortical reaction  Cortical Reaction  Releases enzymes that  Inactivate sperm receptors  Harden zona pellucida

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fertilization  Cleavage  Series of cell divisions  Produces daughter cells  Differentiation  Involves changes in genetic activity of some cells but not others

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Gestation  Induction  Cells release chemical substances that affect differentiation of other embryonic cells  Can control highly complex processes  Gestation  Time spent in prenatal development  Consists of three integrated trimesters, each 3 months long

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester  Cleavage  Sequence of cell divisions begins immediately after fertilization  Zygote becomes a pre-embryo, which develops into multicellular blastocyst  Ends when blastocyst contacts uterine wall

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester  Blastomeres  Identical cells produced by cleavage divisions  Morula  Stage after 3 days of cleavage  Pre-embryo is solid ball of cells resembling mulberry  Reaches uterus on day 4

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester  Blastocyst  Formed by blastomeres  Hollow ball with an inner cavity  Known as blastocoele

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester  Trophoblast  Outer layer of cells separate outside world from blastocoele  Cells responsible for providing nutrients to developing embryo

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester  Inner Cell Mass  Clustered at end of blastocyst  Exposed to blastocoele  Insulated from contact with outside environment by trophoblast  Will later form embryo

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester Figure 29–2 Cleavage and Blastocyst Formation.

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester  Gastrulation  Formation of third layer of cells  Cells in specific areas of surface move toward central line  Known as primitive streak

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester  Primitive Streak  Migrating cells leave surface and move between two layers  Creates three distinct embryonic layers, or germ layers  Ectoderm: consists of the superficial cells that did not migrate into interior of inner cell mass  Endoderm: consists of cells that face blastocoele  Mesoderm: consists of poorly organized layer of migrating cells between ectoderm and endoderm

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester  Embryonic Disc  Oval, three-layered sheet  Produced by gastrulation  Will form body of embryo  Rest of blastocyst will be involved in forming extraembryonic membranes

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester  Embryogenesis  Body of embryo begins to separate from embryonic disc  Body of embryo and internal organs start to form  Folding, differential growth of embryonic disc produces bulge that projects into amniotic cavity  Projections are head fold and tail fold  Organogenesis  Process of organ formation

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester Figure 29–7b The First Trimester.

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The First Trimester Figure 29–7c The First Trimester.

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Labor  Dizygotic Twins  Also called fraternal twins  Develop when two separate oocytes were ovulated and subsequently fertilized  Genetic makeup not identical  70% of twins

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Labor  Monozygotic Twins  Identical twins  Result either from  Separation of blastomeres early in cleavage  Splitting of inner cell mass before gastrulation  Genetic makeup is identical because both formed from same pair of gametes

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Labor  Conjoined Twins  Siamese twins  Genetically identical twins  Occurs when splitting of blastomeres or of embryonic disc is not completed

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Labor  Rates of Multiple Births  Twins in 1 of every 89 births  Triplets in 1 of every 89 2 (7921) births  Quadruplets in 1 of every 89 3 (704,969) births